/* $NetBSD: heap.c,v 1.1.1.2 2012/09/09 16:08:00 christos Exp $ */ /* * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC") * Copyright (c) 1997,1999 by Internet Software Consortium. * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ /*% * Heap implementation of priority queues adapted from the following: * * _Introduction to Algorithms_, Cormen, Leiserson, and Rivest, * MIT Press / McGraw Hill, 1990, ISBN 0-262-03141-8, chapter 7. * * _Algorithms_, Second Edition, Sedgewick, Addison-Wesley, 1988, * ISBN 0-201-06673-4, chapter 11. */ #if !defined(LINT) && !defined(CODECENTER) static const char rcsid[] = "Id: heap.c,v 1.4 2006/03/09 23:57:56 marka Exp "; #endif /* not lint */ #include "port_before.h" #include #include #include #include "port_after.h" #include /*% * Note: to make heap_parent and heap_left easy to compute, the first * element of the heap array is not used; i.e. heap subscripts are 1-based, * not 0-based. */ #define heap_parent(i) ((i) >> 1) #define heap_left(i) ((i) << 1) #define ARRAY_SIZE_INCREMENT 512 heap_context heap_new(heap_higher_priority_func higher_priority, heap_index_func index, int array_size_increment) { heap_context ctx; if (higher_priority == NULL) return (NULL); ctx = (heap_context)malloc(sizeof (struct heap_context)); if (ctx == NULL) return (NULL); ctx->array_size = 0; if (array_size_increment == 0) ctx->array_size_increment = ARRAY_SIZE_INCREMENT; else ctx->array_size_increment = array_size_increment; ctx->heap_size = 0; ctx->heap = NULL; ctx->higher_priority = higher_priority; ctx->index = index; return (ctx); } int heap_free(heap_context ctx) { if (ctx == NULL) { errno = EINVAL; return (-1); } if (ctx->heap != NULL) free(ctx->heap); free(ctx); return (0); } static int heap_resize(heap_context ctx) { void **new_heap; ctx->array_size += ctx->array_size_increment; new_heap = (void **)realloc(ctx->heap, (ctx->array_size) * (sizeof (void *))); if (new_heap == NULL) { errno = ENOMEM; return (-1); } ctx->heap = new_heap; return (0); } static void float_up(heap_context ctx, int i, void *elt) { int p; for ( p = heap_parent(i); i > 1 && ctx->higher_priority(elt, ctx->heap[p]); i = p, p = heap_parent(i) ) { ctx->heap[i] = ctx->heap[p]; if (ctx->index != NULL) (ctx->index)(ctx->heap[i], i); } ctx->heap[i] = elt; if (ctx->index != NULL) (ctx->index)(ctx->heap[i], i); } static void sink_down(heap_context ctx, int i, void *elt) { int j, size, half_size; size = ctx->heap_size; half_size = size / 2; while (i <= half_size) { /* find smallest of the (at most) two children */ j = heap_left(i); if (j < size && ctx->higher_priority(ctx->heap[j+1], ctx->heap[j])) j++; if (ctx->higher_priority(elt, ctx->heap[j])) break; ctx->heap[i] = ctx->heap[j]; if (ctx->index != NULL) (ctx->index)(ctx->heap[i], i); i = j; } ctx->heap[i] = elt; if (ctx->index != NULL) (ctx->index)(ctx->heap[i], i); } int heap_insert(heap_context ctx, void *elt) { int i; if (ctx == NULL || elt == NULL) { errno = EINVAL; return (-1); } i = ++ctx->heap_size; if (ctx->heap_size >= ctx->array_size && heap_resize(ctx) < 0) return (-1); float_up(ctx, i, elt); return (0); } int heap_delete(heap_context ctx, int i) { void *elt; int less; if (ctx == NULL || i < 1 || i > ctx->heap_size) { errno = EINVAL; return (-1); } if (i == ctx->heap_size) { ctx->heap_size--; } else { elt = ctx->heap[ctx->heap_size--]; less = ctx->higher_priority(elt, ctx->heap[i]); ctx->heap[i] = elt; if (less) float_up(ctx, i, ctx->heap[i]); else sink_down(ctx, i, ctx->heap[i]); } return (0); } int heap_increased(heap_context ctx, int i) { if (ctx == NULL || i < 1 || i > ctx->heap_size) { errno = EINVAL; return (-1); } float_up(ctx, i, ctx->heap[i]); return (0); } int heap_decreased(heap_context ctx, int i) { if (ctx == NULL || i < 1 || i > ctx->heap_size) { errno = EINVAL; return (-1); } sink_down(ctx, i, ctx->heap[i]); return (0); } void * heap_element(heap_context ctx, int i) { if (ctx == NULL || i < 1 || i > ctx->heap_size) { errno = EINVAL; return (NULL); } return (ctx->heap[i]); } int heap_for_each(heap_context ctx, heap_for_each_func action, void *uap) { int i; if (ctx == NULL || action == NULL) { errno = EINVAL; return (-1); } for (i = 1; i <= ctx->heap_size; i++) (action)(ctx->heap[i], uap); return (0); } /*! \file */